What is the primary function of SDN via Controller APIs?
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It provides SDN functionality in the form of programmability and centralized control, while supporting legacy devices.
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What is the primary function of SDN via Controller APIs?
It provides SDN functionality in the form of programmability and centralized control, while supporting legacy devices.
What are the three types of APIs mentioned in SDN?
User application API, Controller API, and Policy API.
What distinguishes imperative systems from declarative systems?
Imperative systems require the user to specify how to perform a task, while declarative systems require the user to specify what needs to be accomplished, leaving the method to the system.
What is an active area of research in SDN?
Controlling network behavior via policy.
What becomes important when multiple SDN applications run on a single controller?
Application prioritization and flow handling.
What are the two main alternatives for software SDN devices?
Open vSwitch (OVS) from Nicira and Indigo from Big Switch.
Can applications communicate directly with devices in SDN?
Yes, applications may communicate with devices directly without using a controller.
What is the purpose of policy-level APIs in SDN?
They address network configuration from a declarative perspective, focusing on policies rather than individual device capabilities.
What is one distinct advantage of SDN via APIs?
It works with legacy switches without requiring upgrades to OpenFlow-enabled switches.
What is the emerging standard for the northbound API aimed at?
Developing reusable applications across a wide range of controllers.
What is a characteristic of white box switches?
They are built primarily from merchant silicon switching chips and a commodity CPU and memory by a low-cost Original Device Manufacturer (ODM).
What are VTEPs in the context of SDN?
Virtual Tunnel Endpoints that encapsulate traffic for virtual networks.
What traditional methods have been used to set configuration parameters on devices?
CLI (Command Line Interface) and SNMP (Simple Network Management Protocol).
How do policy-based API solutions benefit SDN applications?
They provide a level of abstraction that shields the SDN application from the complexities of interacting with specific devices.
How do APIs improve agility and automation in SDN?
They allow for quick and automatic responses to changes in the network.
What is Boulder in the context of SDN?
An intents-based northbound interface (NBI) that supports application communication of network changes.
How do legacy switches operate in relation to OpenFlow?
They may operate in both legacy mode and OpenFlow mode.
What do virtual links represent in SDN?
Tunnels interconnecting virtual tunnel endpoints (VTEPs).
What are the drawbacks of using CLI and SNMP for device configuration?
They can be cumbersome and difficult to maintain.
What are the two alternate categories of SDN implementations mentioned?
SDN via APIs and SDN via Hypervisor-Based Overlay Networks.
What is an example of a declarative API concept in SDN?
The NBI concept of intents, which raises the API level of abstraction for requests.
What do virtualized networks and ports abstract from?
Their physical counterparts below.
What does centralized control in SDN via APIs allow for?
Building an SDN solution using provided APIs on distributed network devices.
What is a challenge when managing flows from multiple SDN applications?
Appropriately interleaving the flows from all applications.
What is the impact of SDN on physical switching infrastructure?
It can be built from OpenFlow-enabled white box switches at a lower cost than established Network Equipment Manufacturers' switches.
What is the purpose of the Control Forwarding Policy in SDN?
To manage how data is forwarded through the network.
What traditional methods can be used to invoke functions on networking devices in SDN via APIs?
SNMP, CLI, or NETCONF.
What does the distinction between Open SDN controllers and SDN via Controller APIs indicate?
The distinction can become blurred, as both approaches can offer intelligent control of hybrid networks.
What runs above the physical network infrastructure?
Virtual network traffic.
What is a potential benefit of increased openness in SDN via APIs?
Applications can exploit the exposed interfaces, although they may be proprietary.
What is a common issue faced by Open SDN controllers?
They suffer from birthing pains common to new technologies.
How does flow granularity differ between edge and core devices?
Flows are more fine-grained at the edge and more coarse at the core.
How are flows processed in an SDN device?
In priority order, with the first matching flow acted upon.
What newer mechanism may be used in SDN via APIs?
RESTful APIs.
What is the purpose of the Northbound API in SDN?
It allows applications to interact with the SDN controller, affecting network operations.
What is the role of hypervisors in virtual networks?
They inject traffic into the virtual network and receive traffic from it.
How do hypervisor-based overlay networks benefit data centers?
They address MAC address explosion, VLAN limitations, and improve agility and automation.
What is a limitation of API-based SDN methods?
There may be no controller, requiring direct interaction with each switch.
Which two controllers have assumed dominant roles for commercial applications?
ODL (OpenDaylight) and ONOS.
What type of policies are applied in core devices?
Policies that apply to aggregated flows rather than user-centric policies.
What are the responsibilities of SDN applications?
Managing flow entries, configuring flows, balancing traffic, reacting to topology changes, and redirecting traffic for security tasks.
What is the primary function of the SDN controller?
To provide core functionality between raw interfaces and applications.
What is the significance of hypervisor-based overlay networks in SDN?
They allow virtualized overlay networks to be instantiated across the physical network without concern for the underlying infrastructure.
What does the southbound API do in an SDN controller?
It interfaces with SDN devices.
What is a Tunnel Endpoint or Virtual Tunnel Endpoint (VTEP)?
The edge of the virtual network where packets are encapsulated.
What methods can be invoked through the Northbound API?
Methods may drop, modify, or forward packets, or add, delete, or modify flows.
What is the benefit of using the controller API in SDN applications?
Applications can read information about nodes and links without performing device and host discovery.
What issue does encapsulation in SDN help to solve?
It hides host MAC addresses within the encapsulated frame.
What are the advantages of proprietary alternative controllers?
They offer automation and programmability advantages while providing support for network equipment.
What is the role of the SDN controller?
It maintains a view of the entire network, implements policy decisions, controls SDN devices, and provides a northbound API for applications.
What is necessary for a simple layer two learning switch to function in SDN?
Additional logic to react to new MAC addresses and update forwarding tables.
What is the primary method used for making API calls across networks for computational tasks?
RESTful APIs.
What types of devices does the SDN controller discover?
End-user devices (like laptops and mobile devices) and network devices (like switches and routers).
What is a key functional improvement provided by SDN?
Programmability and centralized control.
What is the primary protocol used in the southbound API for Open SDN?
OpenFlow.
Why is standardization of the Northbound API important?
It enables a plug-and-play environment for SDN applications across different controllers.
What mechanism allows virtual networks to exist above physical infrastructure?
Tunneling, which uses encapsulation.
Which existing routing protocols are mentioned as being used with SDN?
Border Gateway Protocol (BGP), BGP Link State (BGP-LS), and Path Computation Element Protocol (PCE-P).
Why are VLANs not required in hypervisor-based overlay networks?
Because all traffic is tunneled, allowing for tenant isolation without VLANs.
What is a significant challenge for centralized SDN controllers?
Coordination between applications and the lack of a standard northbound API.
What does the ONF workgroup focus on?
The standardization of the northbound API.
What protocol does REST use to pass web traffic?
HyperText Transfer Protocol (HTTP).
What does programmability in SDN allow for?
The opportunity for applications to automate processes and provide dynamic control.
What is the purpose of Network Device Topology Management?
To maintain information about the interconnection details of network devices and end-user devices.
What is a major drawback of using NETCONF or similar APIs in SDN?
It precludes an abstraction layer above.
What are some alternative protocols to OpenFlow in southbound APIs?
BGP, Cisco CLI, and SNMP.
What are some examples of open source SDN controllers?
NOX, Beacon, Floodlight, and Trema.
What is MAC-in-IP tunneling?
A method where the entire frame is encapsulated within a unicast IP frame.
What is NETCONF used for in the context of SDN?
It is a device management and configuration protocol favored by vendors and customers.
What issue arises when using NETCONF-based APIs?
They may not provide an abstract, network-wide view to the programmer.
What is a limitation of hypervisor-based overlay networks?
They do not address existing issues within the physical infrastructure.
What is a potential solution for scaling issues in Open SDN environments?
Implementing standards mandated by bodies like the ONF.
Why might a single standard NBI not be universally needed?
Different ecosystems may grow around each controller, similar to Windows and OSX.
What is one advantage of RESTful APIs regarding firewall configurations?
They require no special firewall configuration as they use a standard TCP port.
What does centralized control in SDN enable?
Applications to have views of the entire network for optimal policy-based forwarding and routing decisions.
What does Flow Management involve in an SDN controller?
Maintaining a database of flows and coordinating with devices to ensure synchronization.
What must the SDN controller and application programmer synchronize with?
The distributed control plane operating on each switch.
Which companies have their own methods for MAC-in-IP tunneling?
Cisco (VXLAN), Microsoft (NVGRE), and Nicira (STT).
What language is used to define data models in NETCONF?
YANG data definition language.
What is the significance of OpenFlow in the context of southbound APIs?
It is the best example of standardization in the southbound interface.
What is OpenDaylight?
An open source SDN controller built by a consortium of vendors.
What common application modules are often bundled with SDN controllers?
Learning switch, router, basic firewall, and simple load balancer.
What does the IETF's Interface to the Routing System (I2RS) provide?
An interface between routing protocols and the Routing Information Base (RIB).
What is the strategy behind SDN via Device APIs?
To provide a richer set of control points on devices for centralized software manipulation.
What is a flow cache in the context of an SDN controller?
A local maintenance of flow statistics that mirrors the flow tables on different switches.
What is a common issue with proprietary APIs in SDN?
They often only work with devices from a specific vendor or a small group of compatible vendors.
How does RESTCONF relate to NETCONF?
RESTCONF bundles NETCONF requests into easier-to-use REST messages.
What is typically added to a hypervisor to enable virtual network capability?
A virtual switch.
What does Chuck Robbins, Cisco CEO, imply about the future of SDN?
He states that 'Everything we build will be programmable,' recognizing the impact of SDN.
What are OF-Config and OVSDB used for?
They are open protocols for the southbound interface, limited to configuration roles.
Which SDN controller is gaining traction in the carrier market?
Open Network Operating System (ONOS).
What is the primary function of an SDN application?
To perform specific functions such as load-balancing or firewalling.
What are the four key drivers inspiring the I2RS protocol?
How do vendors enhance SDN via Device APIs?
By providing an enhanced level of APIs on their devices beyond traditional CLI and SNMP.
How can SDN controllers be tailored to individual network requirements?
By implementing functions via pluggable modules.
What challenges remain in the physical infrastructure despite using overlays?
Manual configuration, maintenance, traffic prioritization, and efficiency issues.
How can the limitation of proprietary APIs be circumvented?
By extending support for multiple vendors’ APIs to mask differences.
What is a key feature of the OpenDaylight (ODL) controller?
It supports multiple southbound protocols.
What types of SDN controllers do vendors like NEC, IBM, and HP offer?
Primarily OpenFlow implementations.
What is the current deficiency in SDN regarding northbound interfaces?
The lack of a standard for the controller-to-application interface.
What does the virtual network topology consist of?
Virtual switches interconnected by virtual point-to-point links.
What did AT&T plan regarding network functions in the next five years?
To move 75% of their critical future functions to a new software-defined architecture.
How does an SDN application respond to events?
By registering as a listener for certain events and invoking callback methods when those events occur.
How does SDN via Controller APIs promote programmability?
By providing a centralized platform from which to build SDN applications using the controller's APIs.
In the context of SDN via Device APIs, what role does the controller play?
It is optional and adds little or no value to the communication between the application and device.
How can the overlay strategy be beneficial for new physical networks?
It can be implemented over a new physical network with simpler switches.
What is the role of the northbound API in SDN?
To provide access to network devices in a common and consistent manner.
What is the benefit of having a single northbound API despite incompatible device interfaces?
It simplifies the application development process.
Which southbound protocols are supported by ODL?
OpenFlow, NETCONF, and BGP-LS/PCE-P.
What programming languages can interfaces to SDN controllers be offered in?
In the language of the controller or alternatives like REST or Python.
What is a key aspect that needs to be addressed for successful SDN deployments?
Experience with a wider array of applications and heterogeneous equipment types.
What types of events can an SDN application handle?
End-user Device Discovery, Network Device Discovery, and Incoming Packet events.
What is a fundamental distinction between Open SDN and SDN via Controller APIs?
The southbound protocols used; Open SDN uses OpenFlow, while SDN via Controller APIs uses legacy protocols repurposed for SDN functionality.
What is one of the benefits of using overlays in SDN?
The ability to build a virtual network on top of an existing physical one.
What is the concept of Hypervisor-Based Overlay Networks in SDN?
It involves creating virtualized networks above the existing physical network without changing its configuration.
What types of events does the SDN controller communicate to applications?
Events related to individual packets or state changes in the network topology.
What do ODL evangelists argue about northbound APIs?
They can be developed to manage hybrid sets of devices.
What is the significance of flow prioritization in SDN?
It is crucial for managing network traffic effectively.
What happens when there is no matching flow entry for an incoming packet?
The default action is usually to forward the packet to the controller.
What is one goal of implementing APIs at the controller level?
To provide a level of abstraction between devices and applications.
What opportunities do northbound APIs present?
Opportunities for innovation and collaboration among vendors and the open source community.
What is the significance of network abstraction layers in SDN?
They help in provisioning, configuration management, and automation for networks.
What do hypervisor-based virtualized networks obscure?
The details of the physical network from the devices that connect to the overlays.
What are default flow entries in an SDN application?
Static flows that are typically the same for every class of discovered network device.
What is an example of information that can be gathered using controller-level APIs?
Topology information about devices in the network.
What types of APIs does the Floodlight controller provide?
A Java API and a RESTful API.
What remains unchanged in the Hypervisor-Based Overlay Networks approach?
The current physical network and its configurations.
What distinguishes Open SDN from other SDN methods?
Open SDN refers to the original definition of SDN, emphasizing its architecture and control mechanisms.
How does the SDN controller abstract device protocols?
It allows applications to communicate with SDN devices without knowing the nuances of those devices.
What do SDN applications utilize in Hypervisor-Based Overlay Networks?
The resources of the overlay networks.
What is one strength of the SDN architecture?
The ability to control switching decisions through a rich family of applications.
What role do external inputs play in SDN applications?
They provide additional data that can influence application behavior and responses.
What is the significance of state information in SDN applications?
It allows for variable responses based on the current context or user state.
